1. Field of the Invention
The present invention generally relates to the field of optical fibers, in particular the present invention relates to an improved device and method for peeling the matrix material from fiber optic ribbons at either the end of a ribbon, or for midspan entry of the ribbon.
2. Discussion of Related Art
In the field of fiber optics the use of fiber optic ribbons has become increasingly popular. An optical fiber ribbon is a collection of optical fibers, usually in the range of 2-48 individual optical fibers, arranged such that the fibers are laid next to each other in the same plane, where the fibers are substantially parallel to each other. This is in contrast to using individual fibers loosely in a optical fiber network. The fibers are all secured to each other through a common ribbon matrix, which is usually a synthetic resin cured over the fibers.
The use of optical fiber ribbons allows for an increase in fiber packing density within a given space. This is extremely advantageous as higher packing densities allow for more fiber to be placed in a given diameter cable and thus more efficient use of existing cable ducts. Further, the use of fiber optic ribbons provide easier fiber identification, maintenance and splicing when working on the fibers. As the advantages of using fiber optic ribbons becomes more widely accepted, ribbon sizes are increasing. This is particularly true with the advent of splittable ribbon units.
A typical fiber optic splittable ribbon unit 10 is shown in FIG. 1, where two or more individual fiber ribbons 11, 12 (for example having twelve fibers 14 each) are joined together with a common matrix material 13 during the manufacturing process to create a wider ribbon (twenty-four fibers). This use of these splittable fiber units allows a single twenty-four fiber ribbon (for example) to be split into two equal twelve fiber portions without compromising the remaining matrix material around the individual twelve fiber ribbons.
However, the use of wider ribbons, or splittable ribbon units, is not without its disadvantages. When installing, repairing or maintaining a fiber optic network there is, on occasion, a need to splice the individual fibers, or otherwise expose the individual fibers. This can be done at either an end of a fiber ribbon, for splicing the fibers to another ribbon or for securing the fibers to a transmission/receiving unit, or along the length of the ribbon (not at an end), to break out only a few of the fibers.
To do these operations it is required to xe2x80x9cpeel backxe2x80x9d or otherwise remove the ribbon matrix material which secures all of the fibers together and holds them in the ribbon form. In the prior art there are many methods to do this, such as manual stripping, chemical stripping, or adhesive stripping. Adhesive stripping is where the ribbon is secured to an adhesive tape or liquid adhesive, which is placed on a flat peel board, and the ribbon is pulled away from the adhesive and peel board, thus causing a portion of the matrix material to remain on the adhesive and board, thereby exposing the individual fibers for access. A typical example of this ribbon peeling process is shown in U.S. Pat. No. 5,460,683 to Beasley, Jr. et al., which is incorporated herein by reference.
The prior-art methods described above have the drawback of creating an angle in the centerline of the fibers contained within the ribbon which is translated into signal attenuation if any of these fibers are live (carrying a signal) at the time of access. Although these methods are acceptable when the ribbon is of a relatively small width, or is not a splittable ribbon unit (having more than one ribbons connected to each other), when the ribbon is wide, the above methods have several drawbacks in addition to the bend angle induced in the fiber. This is particularly true with the adhesion method of peeling a ribbon. This is because of the tendency of the individual performing the peel to favor one side or the other, thereby creating an uneven peel force distribution across the width of the ribbon. For example, if the individual who is peeling the ribbon twists his/her wrist to one side or the other, the ribbon will be subjected to a difference in peel force across its width. Although this also exists in smaller width ribbons, it""s impact is less than on wider ribbons. In the wider ribbons or splittable ribbon units, an inconsistent peel force can cause problems such as one ribbon of the ribbon unit peeling and another not peeling. This introduces the need for the peel operation to be performed multiple times, greatly decreasing the efficiency of the installation, splicing, etc. of optical ribbons.
The present invention is intended to cure the problems, stated above, with peeling the matrix material off of wider ribbons and splittable ribbon units. This is accomplished by using a peel tool which is a lever device for guiding the peel process to ensure that the peel force is distributed evenly across the entire width of the ribbon to be peeled. The even distribution of the peel force greatly increases the probability of an even peel. It should be noted that the present invention is not intended to completely replace the use of the peel board, but may be used with a peel board, as will be described in more detail below. Additionally, the tool may be operated such that the centerline of the fibers is stationary and the peel board to which the coating (matrix) is adhered is pulled away. This will allow the same peeling process to take place with reduced mechanical stress applied to the fibers.
The present invention is of a lever arm design where the prior art peel board or just the ribbon itself may be placed in the base and/or lever arm of the device, and a ribbon is glued or otherwise adhered to the peel board or base, and to a lever arm on the device. Therefore the ribbon will be adhered to two different opposing surfaces. The lever arm is then lifted away from the peel board or base causing the matrix coating to peel away from the ribbon fibers and thus exposing the fibers. In a preferred embodiment the tool would possess the ability to lightly clamp the ribbon into place on the base side so that the fibers remain on the base without any bend induced by the peeling process. The coating on the face of the ribbon facing the base side of the tool may, or may not be adhered to an adhesive surface on the base. By lifting the lever arm portion, to which one side of the ribbon coating is adhered (but the fibers are not clamped to), the coating on this side can be pulled away from the fibers.
The tool of the present invention can be made in almost any size, it can be made to accommodate existing peel boards, it can be made smaller so as to be easily mobile, it can be made to be used without a peel board so as to be disposable after a single use for emergency repair kits, etc, or it can be made without a peel board so that an adhesive is applied to the surfaces of the tool itself and is removed after use to clean the tool for reuse.
The present invention will allow wider ribbons, particularly splittable ribbon units, to be peeled in a single step, whereas prior art methods require multiple steps because of the uneven peel forces applied. The present invention will also allow for reduced risk of fiber damage and/or temporary attenuation increases introduced by the bending of fibers required in the prior art methods.